x+2y+4z=17 2x+y+z=7 3x+y+2z=11

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x+2y+4z=172x+y+z=73x+y+2z=11x+2y+4z=172x+y+z=73x+y+2z=11x+2y+4z=172x+y+z=73x+y+2z=11X+2Y+4Z=17.①2X+Y

x+2y+4z=17 2x+y+z=7 3x+y+2z=11
x+2y+4z=17 2x+y+z=7 3x+y+2z=11

x+2y+4z=17 2x+y+z=7 3x+y+2z=11
X+2Y+4Z=17.①
2X+Y+Z=7.②
3X+Y+2Z=11.③
③-②,得:
x+z=4.④
②+③-①,得:
4x-z=1...⑤
④+⑤,得:
5x=5
x=1
代入④,得:
1+z=4
z=3
再代入②,得:
2+y+3=7
y=2

将上面的三个式子标为①②③,然后用③-②,可得出X+Z=4标为④,再②乘以2得4X+2Y+2Z=14标为⑤,用⑤减去①得3X-2Z=-3,标为⑥,再用④和⑥连解就可以得出Z=3,X=1.再代入①或②或③,就可以解出Y=2.